Vertebral fixing system

ABSTRACT

A vertebral fixing system comprising a connecting part with two longitudinal elements coupled to each other at a first end and having mutually facing recesses for receiving a rod. A portion of a flexible ligature extends through orifices of the two longitudinal elements to define a loop opposite two free ends of the flexible ligature. The two longitudinal elements are engaged at a second end of the connecting part via a locking means. When the two longitudinal elements of the connecting part are locked at the second end of the connecting part, two strands of the flexible ligature are pinched between the rod and a wall of the mutually facing recesses of the two longitudinal elements of the connecting part, preventing the flexible ligature from moving in translation relative to the connecting part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims foreign priority benefits under 35 U.S.C. §119to International Application No. PCT/FR2006/050898, filed Sep. 18, 2006,which claims priority to French Application Nos. FR 0650609, filed Feb.22, 2006, and FR 0509570, filed Sep. 29, 2005. All applications listedherein are incorporated by reference in their entireties.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to vertebral fixing system suitable forbeing mounted on a vertebra.

An intended field of application is particularly, but not exclusively,the treatment of scoliosis, or more generally correcting abnormalcurvatures of the spine.

BACKGROUND OF THE RELATED ART

The spine is constituted by superposed vertebrae that are normally inalignment along a vertical axis, going from the lumbar vertebrae to thecervical vertebrae, each vertebra presenting a posterior wall from whichthere projects a spinous process and two sides having walls from whichthere project the ribs and/or transverse processes. When the spine of anindividual presents abnormal curvature, the vertebrae are inclinedrelative to one another and relative to said vertebral axis. The sidesof the vertebrae situated on one side are thus moved closer togetherforming a concave side, whereas the sides of the vertebrae on the otherside are spaced apart from one another and form a convex side.

In order to straighten the spinal column, the sides of the vertebrae onthe concave side are spaced apart from one another and moved relative toone another to distances that are substantially equivalent to thosebetween the sides of the vertebrae on the other side. In order to keepthe vertebrae in that relative positioning, known devices have screwsthat are inserted in the vertebrae or hooks that are inserted along theinside wall of the vertebral canal, and rods that are forinterconnecting the screws or the hooks.

The hooks are generally inserted in pairs into each vertebra and oneither side close to the pedicles, with their heads projecting from theposterior wall of the vertebra, one on either side of the spinousprocess. By way of example, the heads form a socket suitable forreceiving a rod that is held in place by means of a nut screwed onto thehead so as to press against the rod. The rows constituted by the headsof the hooks situated on either side of the spinous processes areinterconnected and held in a fixed position by two rods that areparallel to each other and to the axis of the spine.

SUMMARY OF THE INVENTION

Nevertheless, it is difficult to use such hooks since the operator mustunder no circumstances interfere with the spinal cord that extends alongthe center of the vertebral canal, since otherwise there is a danger ofparalyzing the patient.

The use of screws makes it possible to diminish the risks of theoperation. The screws likewise have socket-forming heads and they areinserted in pairs into the posterior walls of the vertebrae in thepedicles on either side of the spinous process. Thus, the screwsconstitute points for fixing the vertebrae so as to hold them relativeto one another. Nevertheless, they are necessarily introduced into thepedicles of the vertebrae, and under certain circumstances such pediclescan be small in size or damaged.

SUMMARY OF THE INVENTION

The problem that arises and that the present invention seeks to solve ishow to establish fixing points when it is not possible to introducescrews into the vertebrae in the curved portion of the spine and whenthe use of hooks is too dangerous. PCT patent application WO 2004/010881in the name of the Applicant describes a vertebral fixing system thatenables the problem to be solved.

That vertebral fixing system adapted to be mounted on a vertebra of thespine to connect it to a rod comprises:

-   -   a connecting part placed facing said rib and/or said transverse        process and suitable for being connected to said rod;    -   an elongate flexible ligature suitable for connecting together        said connecting part and at least one rib and/or one transverse        process; and    -   adjustable locking means fastened to said connecting part, said        ligature having a first end secured to said connecting part and        a free second end suitable for sliding in said connecting part        to form a loop, said locking means being suitable for holding in        a fixed position both said connecting part relative to said rod,        and a length of said ligature between said ends that is suitable        for being prevented from moving in translation relative to said        connecting part by said adjustable locking means, whereby the        loop presents a length that is determined so as to prevent        relative displacement of said rod and said vertebra in opposite        directions.

That system is satisfactory, but under certain circumstances it canpresent the following drawback. When the surgeon exerts traction on thefree end of the flexible ligature, the ligature can be jammed byfriction against the bottom face of the process. Under suchcircumstances, it will be understood that although the length of theligature between the bottom face of the process and the zone wheretraction is applied to the ligature is indeed under tension, the lengththat extends between the end of the ligature that is secured to theelongate passageway and the bottom face of the process is not undertension. Thus, overall, the ligature does not perform its function offastening to the vertebra in appropriate manner.

An object of the present invention is to provide a vertebral fixingsystem that enables the above-mentioned drawbacks to be avoided and thatprovides controlled locking of the ligature.

According to the invention, to achieve this object, the vertebral fixingsystem suitable for being mounted on a vertebra of the spine in order toconnect it to a rod comprises:

-   -   a connecting part presenting first and second sides and suitable        for being connected to said rod;    -   a flexible ligature of elongate shape suitable for connecting        together said connecting part and at least one rib and/or        transverse process and/or a portion of the posterior arc of a        vertebra; and    -   adjustable locking means mounted on said connecting part;

and said system is characterized in that:

-   -   said ligature presents two free ends;    -   said connecting part defines at least one passageway for passing        said ligature in such a manner that two distinct strands of said        ligature can be engaged in said passageway(s) so that said two        ligature strands define a first ligature portion forming a loop        that extends from a first side of said connecting part, and        second and third ligature portions extending from the other side        of said connecting part between respective ones of said ligature        strands and said free ends; and    -   said locking means are distinct from the connecting part and        co-operate therewith by screw-fastening, said locking means        being capable of taking a first position relative to the        connecting part in which the two ligature strands are free in        said strand-passing passageway(s), a second position relative to        the connecting part in which the two ligature strands are        prevented from moving in translation relative to the connecting        part, and intermediate positions in which a coefficient of        friction is created between said ligature strands and said        connecting part.

It will be understood that because the two ligature strands that are oneither side of the transverse process are both placed in one or morepassageways, when the locking means are brought into their lockingposition, both ligature strands can be used to exert the tension neededfor fixing to the vertebra by means of a rib and/or a portion of theposterior arc of a vertebra and/or a transverse process.

In addition, since the locking means co-operate with the connecting partby screw-fastening, the “dimensions” of the passageways can be definedaccurately during the various stages of clamping and then locking theligature.

Preferably, the connecting part defines a single passageway and bothligature strands are engaged in the single passageway.

Also preferably, the single passageway is defined firstly by the outsidesurface of the portion of the rod that is engaged in the connecting partand secondly by a wall of the connecting part, and the locking means aresuitable for modifying the section of the passageway.

When the locking means are in their second position, this ensureseffective clamping of the two ligature strands, thereby preventing themfrom moving.

In a first embodiment, the connecting part comprises two longitudinalelements having first ends that are hinged together, each of saidlongitudinal elements presenting a recess suitable for receiving aportion of a section of said rod, a wall of said recess co-operatingwith the side surface of said rod to define said passageway for passingsaid ligature strands, said locking means being mounted at the twosecond ends of said longitudinal elements.

In a second embodiment, the connecting part comprises a part that isgenerally U-shaped, suitable for receiving said rod, and having theouter ends of the limbs of the U-shape threaded, and the adjustablelocking means comprise a tapped ring suitable for co-operating with thethread on the U-shaped part, tightening the ring causing the limbs ofthe part to be clamped against the rod.

Preferably, said passageway(s) is/are constituted by the space betweenthe inside wall of the recess formed in said connecting part and theside wall of said rod.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear better onreading the following description of embodiments of the invention givenby way of non-limiting example. The description refers to theaccompanying figures, in which:

FIG. 1 is a perspective view of a first embodiment of a vertebral fixingsystem;

FIGS. 2A, 2B, and 2C are vertical section views of the fixing systemshowing the use of said system as shown in FIG. 1;

FIG. 3 is a face view showing the FIG. 1 fixing system put into place ona vertebra;

FIG. 4 is a perspective view of a second embodiment of the fixingsystem, the ligature not being shown;

FIG. 5 is an exploded view of the connection device of FIG. 4;

FIG. 6 is a plan view of a portion of the FIG. 1 connection device;

FIG. 6A is a section view on line AA of FIG. 6;

FIG. 7 is a face view of the fixing system of the second embodiment; and

FIGS. 7A and 7B are section views on line VII-VII of FIG. 7 showing twoways in which the flexible ligature can be put into place.

DETAILED DESCRIPTION

As shown in FIG. 1, in the first embodiment, the vertebral fixing systemcomprises a connecting part 12, a flexible ligature 14, and adjustablelocking means 16. The flexible ligature 14 is of elongate shape and iscapable of matching the outline of the parts it is to connect together.In this figure, there can also be seen the rod 18 that is to be securedto the vertebra by means of the vertebral fixing system. In the firstembodiment, the connecting part 12 is constituted by two longitudinalelements given respective references 20 and 22, each having a first end22 a, 20 a and a second end 22 b, 20 b.

As can be seen better in FIG. 2A, the longitudinal elements 20 and 22are hinged to each other at their second ends 20 b, 22 b about a pivotpin 24.

In the embodiment described, the locking means are constituted by ascrew 26 having a head 26 a that is engaged in a bore 28 formed in thefirst end 22 a of the longitudinal element 22. The first end 20 a of thelongitudinal element 20 is pierced by a tapped bore 28 for co-operatingwith the threaded shank 26 b of the screw 26. Each longitudinal element20, 22 has an outside face 20 c, 22 c and an inside face 20 d, 22 d. Thelongitudinal elements 20 and 22 are mounted in such a manner that theinside faces 20 d, 22 d of the longitudinal elements face each other.The inside faces 20 d, 22 d of the longitudinal elements 20 and 22 haverespective mutually-facing recesses 30 and 32, each of substantiallysemicylindrical shape. The recesses 30 and 32 define walls 34 and 36which are ruled surfaces having generator lines parallel to the pivotaxis 24. Finally, slots 38 and 40 cause the bottoms of the recesses 30and 32 to communicate with the outside faces 20 c and 22 c of thelongitudinal elements 20 and 22. As explained in greater detail below,the recesses 30 and 32 are for receiving the rod 18 together with astrand of the ligature 14, the slots 38 and 40 serving to pass theligature 14.

With reference to FIGS. 2A to 2C, there follows an explanation of howthe fixing system is used.

In FIG. 2A, there can be seen the longitudinal elements 20 and 22 in thespaced-apart position, a position in which the locking means 16 arenaturally not active, the threaded shank 26 b of the screw 26 not beingengaged in the bore 28. The ligature 14 is engaged in the slots 38 and40 of the longitudinal elements against one portion of the inside wall34, 36 of the recesses 30 and 32. The rod 18 is then introduced into therecess 30 of the longitudinal element 20 so that the two strands 42 and44 of the ligature 14 are disposed between the inside wall of therecesses 30 and 32 and the side face 18 a of the rod 18. These twosurfaces define a passageway 46 for passing the ligature 14 and havingthe strands 42 and 44 of the ligature 14 placed therein.

As shown better in FIG. 2B, the strands 42 and 44 of the ligature definea portion of the ligature 14 that forms a loop 48 that extends beyondthe outside face 20 c of the longitudinal element 20, and also two freeportions 50 and 52 that extend beyond the outside face 22 c of thelongitudinal element 22. When the longitudinal elements 20 and 22 arespaced apart as shown in FIG. 2B, the ligature 14 can slide freely alongthe passageway 46. Once the portion 48 of the ligature 14 forming theloop is placed around the transverse process or a rib or indeed aportion of the posterior arc of a vertebra, the surgeon engages thethreaded shank 26 b of the screw 26 in the tapped bore 28, causing thelongitudinal element 22 to come progressively closer to the longitudinalelement 20. This approach simultaneously reduces the section of thepassageway 46 in which the strands 42 and 44 of the ligature are engagedand simultaneously introduces a certain coefficient of friction betweenthe ligature and respectively the rod 18 and the walls of the recesses30 and 32. Nevertheless, it is still possible for the surgeon to extracttraction on the free ends 50 and 52 of the ligature 14 until sufficienttension is obtained in the ligature around the vertebral process. Oncethe tension in the ligature is sufficient for providing appropriatefastening, the surgeon finishes off tightening the screw 26 in thetapped bore 28, thus locking the longitudinal elements 20 and 22together. Simultaneously, it will readily be understood that the strands42 and 44 of the ligature are pinched between the rod 18 and the wall ofthe recesses 30 and 32.

In this locking position, the rod 18 is thus secured to the ligature 14via the connecting part 12.

It will also be understood that because the surgeon exerts traction onlyon the free ends 50 and 52 of the ligature 14, there is no risk ofjamming between the ligature 14 and the bottom face of the transverseprocess or of the rib, thus guaranteeing that effective fastening isprovided with the transverse process or the rib or indeed a portion ofthe posterior arc of a vertebra.

This is shown in FIG. 3, where reference AT identifies the transverseprocess.

In the above description, both of the strands 42 and 44 of the ligatureare disposed in the recesses 30 and 32 on the same side of the rod 18.This disposition serves to obtain an optimum result. Nevertheless, itwould not go beyond the invention if the strands 42 and 44 of theligature 14 were to be placed on opposite sides of the rod 18. Undersuch circumstances, it should be considered that the outside face 18 aof the rod 18 and the inside walls of the recesses 30 and 32 define twopassageways, respectively for passing each of the strands 42 and 44 ofthe ligature 14.

FIGS. 4 to 7B show a second embodiment of the fixing system.

In these figures, there can be seen the rod 18, the connecting part nowreferenced 12′, and the flexible ligature 14.

In this embodiment, the connecting part 12′ is constituted by a part 50that is generally U-shaped. The inside wall of this part is constitutedby a bottom 52 of substantially semicylindrical shape and by twosubstantially plane portions 54 and 56 that correspond to the two limbsof the part 50. The width l of the recess 58 formed in the part 50 issubstantially equal to the diameter d of the rod 18. On its outside face50 a which is circularly symmetrical about a longitudinal axis of thepart 50, there is provided a thread 60 occupying its upper portion. Thethread 60 is located entirely above the rod 18 when it is put into placein the recess 58. The thread 60 is designed to co-operate with aclamping ring 62 that constitutes the adjustable locking means. Thisring has a slightly frustoconical bore 64 with an inside face 66 thatcarries tapping 68.

It can thus be understood that when the ring 62 is screwed tight on thethreaded portion 60 of the part 50, it deforms the limbs of the part 50elastically, thereby pinching and clamping strands of the ligature 14between the rod 18 and the inside wall(s) of the recess 58, in a mannerexplained below.

As shown better in FIGS. 6 and 6A, the part 50 includes in its bottom 70a passage 72 for passing the ligature 14 in a manner explained below.

With reference to FIGS. 7, 7A, and 7B, there follows a description oftwo different ways of putting the flexible ligature 14 into place insidethe connecting part 12′ in the second embodiment. The side wall of therod 18 and the inside wall of the recess 58 of the part 50 potentiallydefine two passageways 74 and 76 for passing the middle strands of theflexible ligature 14. In the configuration shown in FIG. 7A, only thepassageway 74 is used. Thus, both intermediate strands 42 and 44 of theflexible ligature 14 are disposed in the passage 74. This dispositionpresents all of the advantages described with reference to the firstembodiment.

In the configuration shown in FIG. 7B, the middle strands 42 and 44 ofthe flexible ligature 14 are disposed respectively one in each of thepassageways 76 and 78, i.e. on either side of the rod 18. Thisconfiguration likewise presents all of the advantages described withreference to the first embodiment of the device since the free ends 50and 52 of the ligature 14 are accessible for exerting the desiredtraction in order to obtain suitable clamping on the spinous processprior to locking the clamping ring 62 on the part 52.

This second embodiment presents the advantage of being simpler in designsince it serves in particular to avoid making two longitudinal partsconstituting a kind of clamp hinged on the pin 24.

It will be understood that in both embodiments, the locking means areconstituted by an element that is distinct from the connecting part andthat is removable therefrom. In addition, in both cases, the lockingmeans co-operate with the connecting part by screw engagement. It isthus possible to adjust accurately the dimensions of theligature-passing passageway(s) as defined by the connecting part and therod. In an initial stage, the coefficient of friction between thecoefficient of the ligature and secondly the rod and the connecting partcan be adjusted. In the final stage, very effective clamping of theligature is obtained between the rod and the locking part.

1. A vertebral fixing system, comprising: a connecting part having twolongitudinal elements, wherein the two longitudinal elements are hingedto each other at a first end of the connecting part, wherein the twolongitudinal elements comprise mutually facing recesses for receiving arod there-between, and wherein each of the two longitudinal elements ofthe connecting part has an orifice; a flexible ligature with two freeends, wherein a portion of the flexible ligature extends through theorifices of the two longitudinal elements of the connecting part todefine a loop opposite the two free ends; and a locking means forlocking the two longitudinal elements of the connecting part at a secondend of the connecting part, wherein when the two longitudinal elementsof the connecting part are locked at the second end of the connectingpart, two strands of the flexible ligature are pinched between the rodand a wall of the mutually facing recesses of the two longitudinalelements of the connecting part, preventing the flexible ligature frommoving in translation relative to the connecting part.
 2. A vertebralfixing system according to claim 1, wherein the orifices of the twolongitudinal elements are in communication with the mutually facingrecesses of the two longitudinal elements.
 3. A vertebral fixing systemaccording to claim 1, wherein the orifices of the two longitudinalelements, in conjunction with a portion of the mutually facing recessesof the two longitudinal elements, define a single passage way throughwhich the flexible ligature is engaged with the connecting part.
 4. Avertebral fixing system according to claim 1, wherein when the twolongitudinal elements of the connecting part are not locked at thesecond end of the connecting part, the two strands of the flexibleligature are slidable along a single passageway.
 5. A vertebral fixingsystem according to claim 1, wherein each of the mutually facingrecesses is of substantially semicylindrical shape.
 6. A vertebralfixing system according to claim 1, wherein at least one of the mutuallyfacing recesses comprises a ruled surface.
 7. A vertebral fixing systemaccording to claim 1, wherein the two longitudinal elements are hingedto each other about a pivot pin.
 8. A vertebral fixing system accordingto claim 1, wherein the locking means comprises a head that is engagedin a bore formed in one of the two longitudinal elements.
 9. A vertebralfixing method, comprising: manipulating a portion of a flexible ligaturethrough orifices of two longitudinal elements of a connecting part toform a loop opposite two free ends of the flexible ligature; introducinga rod into mutually facing recesses of the two longitudinal elements ofthe connecting part, wherein two strands of the flexible ligature aredisposed between a side face of the rod and a wall of the mutuallyfacing recesses of the two longitudinal elements of the connecting part;engaging the two longitudinal elements of the connecting part;tensioning the flexible ligature by pulling on the two free ends of theflexible ligature relative to the connecting part; and locking the twolongitudinal elements of the connecting part to prevent the flexibleligature from moving in translation relative to the connecting part. 10.A vertebral fixing method according to claim 9, wherein when the twolongitudinal elements of the connecting part are locked at a second endof the connecting part, the two strands of the flexible ligature arepinched between the side face of the rod and the wall of the mutuallyfacing recesses of the two longitudinal elements of the connecting part.11. A vertebral fixing method according to claim 9, further comprisingplacing the loop around a bony element.
 12. A vertebral fixing methodaccording to claim 9, wherein tensioning the flexible ligature causesthe loop to tighten around a bony element.
 13. A vertebral fixing methodaccording to claim 9, wherein the two longitudinal elements are coupledto each other at a first end of the connecting part.
 14. A vertebralfixing method according to claim 13, wherein engaging the twolongitudinal elements of the connecting part further comprises engagingthe two longitudinal elements of the connecting part with a lockingmeans at a second end of the connecting part.
 15. A vertebral fixingmethod according to claim 14, wherein locking the two longitudinalelements of the connecting part further comprises locking the twolongitudinal elements of the connecting part at the second end of theconnecting part utilizing the locking means.
 16. A vertebral fixingmethod according to claim 15, wherein the locking means comprises a headthat is engaged in a bore formed in one of the two longitudinalelements.
 17. A vertebral fixing method according to claim 13, whereinengaging the two longitudinal elements of the connecting part furthercomprises causing ends of the two longitudinal elements of theconnecting part to come progressively closer to each other.
 18. Avertebral fixing method according to claim 17, wherein causing the endsof the two longitudinal elements of the connecting part to comeprogressively closer to each other simultaneously introduces a certaincoefficient of friction between the ligature and respectively the rodand the wall of the mutually facing recesses of the two longitudinalelements of the connecting part.
 19. A vertebral fixing method accordingto claim 9, wherein prior to the locking step, the flexible ligature isslidable relative to the connecting part.
 20. A vertebral fixing method,comprising: manipulating a portion of a flexible ligature throughorifices of two longitudinal elements of a connecting part to form aloop opposite two free ends of the flexible ligature, wherein the loopis placed around a bony element, and wherein the two longitudinalelements are coupled to each other at a first end of the connectingpart; introducing a rod into mutually facing recesses of the twolongitudinal elements of the connecting part, wherein two strands of theflexible ligature are disposed between a side face of the rod and a wallof the mutually facing recesses of the two longitudinal elements of theconnecting part; engaging the two longitudinal elements of theconnecting part at a second end of the connecting part; tensioning theflexible ligature to fasten the loop around the bony element; andlocking the two longitudinal elements of the connecting part at thesecond end of the connecting part, thereby pinching the two strands ofthe flexible ligature between the side face of the rod and the wall ofthe mutually facing recesses of the two longitudinal elements of theconnecting part.